Method for effecting kickdown shift

Abstract

A method for effecting a kickdown shift in a transmission of an automotive vehicle controls turbine speed change based on a continuous desired acceleration calculation. The method determines an initial speed of a turbine that transmits torque between an engine and a plurality of gears through a plurality of releasing and engaging elements. A target speed of one of the plurality of gears is determined. A desired time required to increase the turbine speed to the target speed is determined. A desired acceleration of the turbine is calculated according to the initial speed, the target speed, and the desired time. Turbine speed change rate is controlled through controlling the clutch torque of one or more of the releasing and engaging elements based on the desired acceleration.

1. A method for effecting a kickdown shift in a transmission of an automotive vehicle, the transmission including a plurality of gears and a torque converter assembly and turbine for transmitting torque between an engine and the plurality of gears through a plurality of engaging and releasing elements, the method comprising:
 determining an initial speed of the turbine; 
 determining a target speed of one of the plurality of gears; 
 determining a desired time required to increase the initial speed to the target speed; 
 calculating a desired acceleration of the turbine according to the initial speed, the target speed, and the desired time; and 
 controlling the torque of one or more releasing and engaging elements based on the desired acceleration. 
 
     
     
       2. The method of  claim 1  wherein the step of calculating the desired acceleration includes calculating the desired acceleration according to a sum of the target speed and an offset speed. 
     
     
       3. The method of  claim 2  further comprising applying an engagement element to said one of the plurality of gears when the turbine speed is approximately equal to the sum of the target speed and the offset speed. 
     
     
       4. The method of  claim 1  wherein the target speed is determined in accordance with a shift event and a target gear ratio. 
     
     
       5. The method of  claim 4  wherein the shift event is determined as a function of vehicle speed and one of throttle position and engine output torque. 
     
     
       6. The method of  claim 1  wherein calculating the desired acceleration includes calculating the desired acceleration according to an exponential decay rate. 
     
     
       7. The method of  claim 1  wherein controlling torque includes controlling the speed of the turbine according to the desired acceleration. 
     
     
       8. The method of  claim 1  further comprising applying an engagement element to said one of the plurality of gears when the turbine speed exceeds the target speed. 
     
     
       9. A method for effecting a kickdown shift in a transmission of an automotive vehicle, the transmission including a plurality of gears and a torque converter assembly having a turbine for transmitting torque between an engine and the plurality of gears through a plurality of releasing and engagement elements, the method comprising:
 determining a shift event based on vehicle speed and one of a throttle position and engine output torque; 
 determining an initial speed of the turbine; 
 determining a target speed of one of the plurality of gears according to the shift event; 
 determining a desired time required to increase the initial speed to the target speed; 
 calculating a desired acceleration of the turbine according to the initial speed, the target speed, and the desired time; and 
 controlling torque of one or more releasing and engaging elements based on the desired acceleration. 
 
     
     
       10. A system for effecting a kickdown shift in a transmission of an automotive vehicle, the transmission including a plurality of gears and a torque converter assembly and turbine for transmitting torque between an engine and the plurality of gears through a plurality of releasing and engagement elements, the system comprising:
 a transmission controller adapted to be coupled to the transmission; 
 a turbine speed sensor transmitting a signal indicative of turbine speed to the transmission controller; and 
 a transmission output speed sensor transmitting a signal indicative of transmission output speed to the transmission controller; 
 wherein the transmission controller is operative: 
 to determine, using the speed sensors, an initial speed of the turbine, a target speed of one of the plurality of gears, and a desired time required to increase the initial speed to the target speed; 
 to calculate a desired acceleration of the turbine as a function of the initial speed, the target speed and the desired time; and 
 to control turbine speed change rate based on the desired acceleration through controlling the torque of one or more releasing and engaging elements. 
 
     
     
       11. The system of  claim 10  wherein the transmission controller is operative to calculate the desired acceleration according to a sum of the target speed and an offset speed. 
     
     
       12. The system of  claim 11  wherein the transmission controller is further operative to apply an engagement element to said one of the plurality of gears when the turbine speed is approximately equal to the sum of the target speed and the offset speed. 
     
     
       13. The system of  claim 10  wherein the transmission controller determines the target speed in accordance with a shift event and a target gear ratio. 
     
     
       14. The system of  claim 13  further comprising a throttle position sensor or pedal position sensor and wherein the transmission controller determines the shift event as a function of vehicle speed and one of throttle positions, pedal position, and engine output torque. 
     
     
       15. The system of  claim 10  wherein the transmission controller calculates the desired acceleration according to an exponential decay rate. 
     
     
       16. The system of  claim 10  wherein the transmission controller controls the turbine speed change rate by controlling the clutch torque of one or more releasing and engaging elements according to the desired acceleration. 
     
     
       17. The system of  claim 10  wherein the transmission controller is further operative to apply an engagement element to said one of the plurality of gears when the turbine speed exceeds the target speed. 
     
     
       18. A vehicle comprising:
 an engine; 
 a transmission including a plurality of gears; 
 a torque converter assembly having a turbine for transmitting torque between the engine and the plurality of gears via a plurality of releasing and engaging elements; and 
 a transmission controller coupled to the transmission and the engine, wherein the transmission controller is operative to: 
 determine an initial speed of the turbine; 
 determine a target speed of one of the plurality of gears; 
 determine a desired time required to increase the initial speed to the target speed; 
 calculate a desired acceleration of the turbine as a function of the initial speed, the target speed and the desired time; and 
 control turbine speed change rate through controlling torque of one or more releasing and engaging elements based on the desired acceleration.